Most present fuel injectors utilize inwardly opening valve members to create a flow path from the injector body into a combustion chamber. One example of a commonly used inwardly opening valve member is described in U.S. Pat. No. 5,522,545 to Camplin et al. The Camplin hydraulically-actuated fuel injector includes a valve member which is biased toward an downward, closed position by a biasing spring. At the initiation of the injection event, high pressure fuel surrounds the valve member and acts on a lifting hydraulic surface of the valve member. When the pressure of the fuel reaches a valve opening pressure, the valve member can move upward, and thus farther inward, against the action of the biasing spring to open a flow path from the fuel injector into the combustion chamber. While the inwardly opening valve member has performed well in fuel injectors, performance of the fuel injectors can sometimes be improved upon and some occasional problems with inwardly opening valve members can be addressed.
There are a few problems that sometimes arise from use of an inwardly opening valve member that can be dramatically reduced with replacement by an outwardly opening valve member. For instance, high combustion chamber pressures can occasionally force undesirable gasses and fluids from the engine cylinder into the fuel injector at the end of the injection event. While this gas ingestion does not occur frequently, when it does occur it is detrimental to injector performance. It is therefore desirable to reduce the likelihood of this gas ingestion. Further, the high tip stress that is created at the end of the injection event caused by impact loading can sometimes lead to tip breakage. This can occur because the impact loads created by the inwardly opening valve member are directed at the thin tip portion of the fuel injector. If the tip becomes weakened from the forces exerted on it by the valve member during the life of the fuel injector, there is a potential for tip breakage which would be fatal to the fuel injector. Therefore, it is desirable to have the impact stress absorbed by the larger portion of the metal component. Finally, it is well known in the art that it is desirable to create the most abrupt stop to the injection event possible in order to reduce noise and emissions created by engines. While the inwardly opening fuel injector has performed well in this regard, the technology can be improved upon to create even better results.
The present invention is directed to overcoming one or more of the problems set forth above and to improving the performance of fuel injector valve members.